Gas detection, particularly detection of a specific gas component in a sample of gases, is traditionally achieved by introducing the gas sample into a gas detector, which often may be a mass spectrometer or electrolytic conductivity detector. Other detection systems may include thermal conductivity, flame ionization, and argon detectors.
Electrolytic conductivity detectors usually provide an electrical signal that is functionally related to the presence of a selected component and typically aid in determining properties of electrolytes in solutions. Such devices often include electrode surfaces with a continuous phase liquid electrolyte in between the electrode surfaces. These detectors generally entail measuring a difference in potential in the electrolytic material before and after the gas exiting the column enters the detector and is absorbed by the electrolytic material. If the gas was mixed with a reactant in the reactor, the reactant may also need to be absorbed in the electrolytic material before providing a detectable electrical signal. A possible disadvantage of the conductivity detector is that absorption by the electrolytic material takes time, which lengthens the detector's response time. The disadvantage may be exacerbated if both the gas and reactant need to be absorbed. Another possible disadvantage is a limited sensitivity of the detector. Because gas is normally detected indirectly, where the difference in potential of the electrolytic material indicates the type and/or concentration of the gas, there may be a measurement error between the electrolytic material measurement and correlating this to the concentration of gas.
A typical conductivity detector is described in U.S. Pat. No. 4,440,726 to Coulson and shown in FIG. 1. Typically, an electrolyte, reactant gas, and gas exiting from the column enter the capillary. Electrodes 24 and 28 are normally placed in the electrolyte solution to measure the difference in potential.
Similar to the conductivity detector, the mass spectrometer and other detection systems of gas chromatography have potentially limiting abilities to detect gas with a high degree of sensitivity. As mentioned in U.S. Pat. No. 6,165,251 to Lemieux et al., detection systems in general have insufficient sensitivity to measure amounts of volatiles in the parts per billion concentration range.
Some gas components may have difficulty being detected by the detector, in which case a reactor may be provided to oxidize and/or reduce the gas sample prior to entering the detector. Generally, the reactor heats the gas sample with a reactant to form a detectable compound. The more completely a gas sample is oxidized and/or reduced, the more likely an accurate concentration of a desired gas component is detected by the detector. Partially oxidizing or reducing the gas sample, and the gas component, may still result in the desired component being detected but may not result in an accurate concentration determination of the desired component. The reactant may be a gas, liquid, or solid and varies according to the desired gas to be detected. Typical reactants include air, hydrogen, and oxygen. A detectable compound is one that generally provides an electrical signal detectable by the detector.
Although it facilitates detection for some gases, the traditional reactor may not enable sufficient detection or efficient oxidation and/or reduction for other gas components. For example, a reactor that reduces an aromatic compound without oxidation typically has difficulty reacting hydrogen with the desired element, such as sulfur, of the aromatic compound. However, oxidizing the aromatic compound is believed to weaken the outer ring structure of the aromatic compound, which may facilitate reduction, or reaction between hydrogen and the desired component, such as sulfur. Therefore, oxidation and reduction may provide a more efficient conversion of the sulfur in the aromatic compound to a detectable component.
Therefore, to provide both oxidation and reduction capabilities to traditional detection systems, two reactors would typically be used, where one reactor may be designated for reducing the gas and the other reactor may be designated for oxidizing the gas.
GB 1,382,640 to Deschamps (“Deschamps”) relates to a method that may oxidize a gas sample in the presence of a catalyst to possibly provide an efficient conversion of sulfur compounds to sulfur dioxide at relatively low temperatures. The invention does not typically relate to efficient conversion during oxidation and reduction.
U.S. Pat. No. 6,309,612 to Balachandran et al. (“Balachandran”) discloses a ceramic membrane reactor which may contact two reactant gases at different pressures. Balachandran discloses that the two reactant gases may be introduced during o7xidation but the invention does not typically relate to a reactor having the capability to oxidize and/or reduce a gas.
U.S. Pat. No. 6,355,150 to Savin-Poncet et al. (“Savin”) discloses a device that may regulate air injected into a reactor for oxidizing hydrogen disulfide to sulfur. However, the invention does not typically relate to a system that has the capability to oxidize and/or reduce a gas.
U.S. Pat. No. 3,934,193 to Hall (“Hall”) discloses a conductivity detector for detecting a gas. Hall includes an invention that may, as shown in FIGS. 8 and 9 and described in col. 8, provide a detector that is capable of operating in the reductive and oxidative modes. Hall may also describe the furnace operating at 820° C. in the reductive mode and 840° C. in the oxidative mode with either hydrogen or oxygen as a reaction gas. However, Hall appears to operate the furnace in either the reductive mode or the oxidative mode and not both. Hence, Hall does not typically describe or show a furnace having the capability of reducing and/or oxidizing a gas sample. In fact, Hall represents the traditional reactor where two reactors may be needed to reduce and oxidize the gas sample.
A possible disadvantage of Deschamps, Balachandran, Savin, and Hall is that two reactors are needed to oxidize and reduce a gas. Another possible disadvantage is that these references may require a catalyst for carrying out the oxidation/reduction.
U.S. Pat. No. 5,985,673 to Bao et al. (“Bao”) appears to relate to a pyrolyzer which may convert sulfur-containing molecules in a gas sample to hydrogen sulfide by oxidizing the gas sample with oxygen and then reducing the gas sample with hydrogen. However, as shown in the prior art represented by FIG. 1, the pyrolyzer may use a gas chromatograph detector, which typically has limited sensitivity, as described above. In addition, Bao typically introduces the two reactants into the gas sample without either premixing the reactants or homogenously mixing the reactants and gas sample, both of which may enhance detection because the desirous gas component may then be detectable in any part of the gas sample.
What is desired, therefore, is an improved reactor that facilitates detection of a gas sample. What is also desired is a reactor having the ability to efficiently oxidize and/or reduce a gas. Another desire is to provide a detection system having improved sensitivity and reduced response time for detecting a gas component.